---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Thu 08/19/10: 11 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 03:47 AM - Re: 447 analysis (Thom Riddle) 2. 05:20 AM - Re: Re: 447 analysis (Richard Girard) 3. 06:54 AM - Re: 447 analysis (David Kulp) 4. 07:46 AM - Re: 447 analysis (Richard Girard) 5. 10:08 AM - Re: 447 analysis (Thom Riddle) 6. 10:44 AM - Re: 447 analysis (rparigor@suffolk.lib.ny.us) 7. 10:45 AM - Re: Re: 447 analysis (Richard Girard) 8. 11:06 AM - Re: 447 analysis (Richard Girard) 9. 03:03 PM - Re: 447 analysis (rparigoris) 10. 05:07 PM - Re: Re: 447 analysis (Richard Girard) 11. 06:27 PM - Re: 447 analysis (dave) ________________________________ Message 1 _____________________________________ Time: 03:47:54 AM PST US Subject: RotaxEngines-List: Re: 447 analysis From: "Thom Riddle" Dave, The one 447 I've owned had the rpm instability in the mid-range like you described but it did not have the half black spark plug nor a wide difference in EGT nor CHT between the two cylinders. I suspect the RPM instability is characteristic of this engine but know that the half black is not. I would ignore the RPM issue until you've discovered and fixed the cause of the half black plug. -------- Thom Riddle Buffalo, NY (9G0) Kolb Slingshot SS-021 Jabiru 2200A #1574 Tennessee Prop 64x32 The world is round; it has no point. - Adrienne E. Gusoff Read this topic online here: http://forums.matronics.com/viewtopic.php?p=309360#309360 ________________________________ Message 2 _____________________________________ Time: 05:20:05 AM PST US Subject: Re: RotaxEngines-List: Re: 447 analysis From: Richard Girard Thom, RPM instability is not a characteristic of a properly set up 447. I suspect that Dave's trouble is prop loading, i.e., the usual suspect, but without more info I can't say for sure. When I do the break in and set up per the Rotax manual so that the prop is pitched to reach the peak HP area of the engines power curve the engine performs without quirks. On an older engine it's tough to say without more info. If nothing else, making sure the prop is right, assuming a ground adjustable, is cheap, quick, and most often effective. Rick On Thu, Aug 19, 2010 at 5:47 AM, Thom Riddle wrote: > > > > Dave, > > The one 447 I've owned had the rpm instability in the mid-range like you > described but it did not have the half black spark plug nor a wide > difference in EGT nor CHT between the two cylinders. I suspect the RPM > instability is characteristic of this engine but know that the half black is > not. I would ignore the RPM issue until you've discovered and fixed the > cause of the half black plug. > > -------- > Thom Riddle > Buffalo, NY (9G0) > Kolb Slingshot SS-021 > Jabiru 2200A #1574 > Tennessee Prop 64x32 > > > The world is round; it has no point. > - Adrienne E. Gusoff > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=309360#309360 > > -- Zulu Delta Kolb Mk IIIC 582 Gray head 4.00 C gearbox 3 blade WD Thanks, Homer GBYM ________________________________ Message 3 _____________________________________ Time: 06:54:31 AM PST US From: David Kulp Subject: Re: RotaxEngines-List: 447 analysis Thanks to both of you for your contributions, Lucien and Rick. I've messed with the load factor and there are times I can get it to pull steady at 48 - 5000, but I seem to be descending (just ordered a digital Attitude Indicator which will make it easier than using the VSI) It's encouraging to know that this part of my question seems to be the "nature of the beast." The 50% tan 50% black spark plug has me a bit more concerned, though. To answer your questions, Rick: The plane sat for pretty close to a year from when I bought it, picked it up and got a home for it. The carb bowl is clean and emptied regularly. The carb socket is supple and sound. The prop is unchanged from when I bought it. I show 6200 at 60 MPH climbout, and I've only run it wide open once straight and level and I believe it was 6800 Rs (being a multi-million mile 18 wheeler jockey I tend to shy away from high RPMs - I even buy motorcycles that are heavy on low RPM torque rather than the high horsepower at high RPM screamers... maybe my mindset is part of the unsettled mid-range question). Hope that info helps your analysis. I sure appreciate your input - I feel so alone up there when I'm concerned there's a problem; you probably know why (20 year anniversary of the incident today!!). Best, Dave Kulp Bethlehem, PA FireFly 11DMK ________________________________ Message 4 _____________________________________ Time: 07:46:52 AM PST US Subject: Re: RotaxEngines-List: 447 analysis From: Richard Girard Dave, If it were me, the first place I thing I would do is crank in a little more prop pitch. I usually set a 447 for 6000 RPM static when tied down on the ground at WOT. This puts the engine near the top of the HP curve, but not at the peak. Like you, I'm uncomfortable setting up an engine so that it can run close to it's WOT red line RPM (6800 RPM for the 447). Anyway, with the engine set for 6000 RPM static, you'll find that WOT throttle, in flight will be about 6400. I recommend, since your engine did sit for a year, that you pull the carb and thoroughly inspect the two idle air bypasses at the floor of the throttle bore. Even a tiny amount of fuel that is allowed to congeal in them will throw off the carb throughout it's range. My 582 drove me nuts trying to tune it up after a year layup while I rebuilt systems on the aircraft. Even though I was careful to drain the float bowls and put in preservative oil, a drop of fuel was all it took to close both those passages and nothing helped until I took a fine needle and a can of carb cleaner worked all the crud out of those two little passages. Put the carbs back on, did a carb synch and no problems since. In summary, pull the carb check passages, all jets and the needle valve, pay attention to the idle air passages. When you're sure the carb is all clean, reinstall and set static airplane RPM for 6000. IF the problem persists, at least you have the basics set properly to you can begin checking other things. Without this basic setup you can chase your tail until you're nuts and never find the problem. Seen that one enough times to know. Good luck. Rick On Thu, Aug 19, 2010 at 8:53 AM, David Kulp wrote: > > Thanks to both of you for your contributions, Lucien and Rick. I've > messed with the load factor and there are times I can get it to pull steady > at 48 - 5000, but I seem to be descending (just ordered a digital Attitude > Indicator which will make it easier than using the VSI) It's encouraging to > know that this part of my question seems to be the "nature of the beast." > The 50% tan 50% black spark plug has me a bit more concerned, though. > > To answer your questions, Rick: The plane sat for pretty close to a year > from when I bought it, picked it up and got a home for it. The carb bowl is > clean and emptied regularly. The carb socket is supple and sound. The prop > is unchanged from when I bought it. I show 6200 at 60 MPH climbout, and > I've only run it wide open once straight and level and I believe it was 6800 > Rs (being a multi-million mile 18 wheeler jockey I tend to shy away from > high RPMs - I even buy motorcycles that are heavy on low RPM torque rather > than the high horsepower at high RPM screamers... maybe my mindset is part > of the unsettled mid-range question). > > Hope that info helps your analysis. I sure appreciate your input - I feel > so alone up there when I'm concerned there's a problem; you probably know > why (20 year anniversary of the incident today!!). > > Best, > > > Dave Kulp > Bethlehem, PA > > FireFly 11DMK > > -- Zulu Delta Kolb Mk IIIC 582 Gray head 4.00 C gearbox 3 blade WD Thanks, Homer GBYM ________________________________ Message 5 _____________________________________ Time: 10:08:57 AM PST US Subject: RotaxEngines-List: Re: 447 analysis From: "Thom Riddle" Rick, On my FS w/ 447, I set the static rpm to 5800 which is more pitch than your recommended 6000 and therefore more loading, and still got the rpm instability that Dave described. I set the pitch several times at various static rpms from 5800 to 6200 and points between and it did not affect this characteristic. All it did was change EGTs, which is what I expected. I never did a thorough inspection/cleaning of the carb because....right after I got it just the way I wanted, except for the inability to hold constant rpm below about 5200 in cruise,... I broke the airplane and sold its remains. do not archive -------- Thom Riddle Buffalo, NY (9G0) Kolb Slingshot SS-021 Jabiru 2200A #1574 Tennessee Prop 64x32 The world is round; it has no point. - Adrienne E. Gusoff Read this topic online here: http://forums.matronics.com/viewtopic.php?p=309420#309420 ________________________________ Message 6 _____________________________________ Time: 10:44:45 AM PST US Subject: Re: RotaxEngines-List: 447 analysis From: rparigor@suffolk.lib.ny.us Hi Group I never worked or flew with a 447. It however sounds like too lean of a mixture. First thing is to identify the exact position of the throttle when it happens, then identify what part of the carb controls things at that time.May be taper or shapeof jet needle or cutaway of slide that is just not right, not just jet needle position. Some needle jets have holes in the side to draw air,could be that too. If easy perhaps you could select the RPM range and richen the mixture to see if it helps out. Easiest is to try enriching circuit, if no change try tosquirting some fuel incab, if no good tryrestricting intake of carb if you can do it safetly. Just some ideas. I remember making a new jet needle for a single carb Cayuna with a similar problem that helped out quite a bit. Ron Parigoris ________________________________ Message 7 _____________________________________ Time: 10:45:00 AM PST US Subject: Re: RotaxEngines-List: Re: 447 analysis From: Richard Girard Thom, with the vagaries of two stroke performance, it could be that all mine were installed on trikes and all were brand new out of the box when I got them so they had no previous abuse. Rick On Thu, Aug 19, 2010 at 12:08 PM, Thom Riddle wrote: > > > > Rick, > > On my FS w/ 447, I set the static rpm to 5800 which is more pitch than your > recommended 6000 and therefore more loading, and still got the rpm > instability that Dave described. I set the pitch several times at various > static rpms from 5800 to 6200 and points between and it did not affect this > characteristic. All it did was change EGTs, which is what I expected. I > never did a thorough inspection/cleaning of the carb because....right after > I got it just the way I wanted, except for the inability to hold constant > rpm below about 5200 in cruise,... I broke the airplane and sold its > remains. > > > do not archive > > -------- > Thom Riddle > Buffalo, NY (9G0) > Kolb Slingshot SS-021 > Jabiru 2200A #1574 > Tennessee Prop 64x32 > > > The world is round; it has no point. > - Adrienne E. Gusoff > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=309420#309420 > > -- Zulu Delta Kolb Mk IIIC 582 Gray head 4.00 C gearbox 3 blade WD Thanks, Homer GBYM ________________________________ Message 8 _____________________________________ Time: 11:06:49 AM PST US Subject: Re: RotaxEngines-List: 447 analysis From: Richard Girard Ron, All I can tell you is that two strokes are different from other engines. Getting the power loading of the engine correct is the first essential thing to do before you even try and evaluate any condition (short of known bad parts like stuck rings, metal transfer caused by seizure, piston damage through detonation. On new engines I've never had to do a thing more that drop the needles one notch. Chasing jet combinations is a fools errand for the most part. Stock Rotax engines work out of the box if you A: break them in per the Rotax schedule and B: Set the prop for the correct power loading. It is B: that sets two strokes apart from other engines. Rick On Thu, Aug 19, 2010 at 12:42 PM, wrote: > Hi Group I never worked or flew with a 447. It however sounds like too lean > of a mixture. First thing is to identify the exact position of the throttle > when it happens, then identify what part of the carb controls things at that > time. May be taper or shape of jet needle or cutaway of slide that is just > not right, not just jet needle position. Some needle jets have holes in the > side to draw air, could be that too. If easy perhaps you could select the > RPM range and richen the mixture to see if it helps out. Easiest is to try > enriching circuit, if no change try to squirting some fuel in cab, if no > good try restricting intake of carb if you can do it safetly. > Just some ideas. I remember making a new jet needle for a single carb > Cayuna with a similar problem that helped out quite a bit. Ron Parigoris > > > * > > * > > -- Zulu Delta Kolb Mk IIIC 582 Gray head 4.00 C gearbox 3 blade WD Thanks, Homer GBYM ________________________________ Message 9 _____________________________________ Time: 03:03:31 PM PST US Subject: RotaxEngines-List: Re: 447 analysis From: "rparigoris" Rick I agree that 2 strokes can be quite different than 4 strokes when it comes to carb tuning. For one thing many don't have an exactly flat torque curve where there is less than optimal combustion taking place at a given RPM range. It could be that all the burnt exhaust gasses are not being expelled from the combustion chamber or that some of the fresh charge is blowing right out the exhaust. The type of exhaust affects power band, as does the intake tuning. BTW I have had great success adding a canister to intake to act as a dampener in several cases with this sort of thing that happens. Yamaha called it a tuned intake. What happens on tune of some 2 strokes is that instead of only sucking through carb, there is a pulse that shoots back out carb a little at certain RPMs. This really screws things up. The canister helps even out this shooting back of airflow. This is usual when engine is out of ideal power band where you are getting a nice fresh charge in cylinder. I agree that first and foremost make sure carb is clean and functioning correctly. (You did remove all jets and make absolute sure no carb snot? Also make sure number on jets is as specified by Rotax). It's true that loading can affect this searching mode. On motorcycles, lets take for example a 1972 Kawasaki H2 3 cylinder two stroke. When you are crusing at 55mph there is little load on motor and motor is not quite in efficient part of torque curve. It would do this hunting trick. I made a pilot controllable air jet where I ran the pilot air screw a little rich with fuel for the 55mph cruise, but you could lean it a bit of other times when you were in stop and go mode. Worked great. Anyway if prop is not loading in a specific install, carb adjustment can quite possible resolve. I forget specifics on motor origin of motor with this problem, but if motor was tuned for higher altitude operation and is now operating at a lower altitude, that will cause a leaner mixture. I also shoehorned a YTZ250 engine in a YZ 80 frame, took tune of motor from 5 ports and 32mm carb to 7 ports and 42mm flat slide pretty close to motocross tune. Again had problems with light loading hunting and made a reach down when riding airscrew adjustment after getting carb set optimal. Worked great. BTW tuning did in fact include getting optimal taper to jet needle. Remember that the exhaust system can greatly effect tune of a two stroke. If it is a tuned exhaust almost always to get optimal performance carb needs tweaking if it was originally tuned for only a muffler. Another often overlooked issue is an exhaust system that changes. On motorcycles with high time carbon coats inside. A slick trick is to light carbon on fire with a oxy acetelene torch, then turn off acetelene and only let oxygen into chamber, watch carbon burn out (cherry red patch). A few taps releases this fine brown/tan residue after carbon stops burning. I have had a handful of subtle tuning issues end up being exhaust related. Not only carbon clogging, but damaged expansion chambers can cause change. Ron Parigoris Read this topic online here: http://forums.matronics.com/viewtopic.php?p=309466#309466 ________________________________ Message 10 ____________________________________ Time: 05:07:27 PM PST US Subject: Re: RotaxEngines-List: Re: 447 analysis From: Richard Girard Yes, the phenomenon of fuel going back up and out the carb, known as fuel stand off, can be a real issue. This problem was the reason for the invention of velocity stacks. Unlike the exhaust port the intake port has to rely on a vacuum pulse to pull that ejected charge back down the throat of the carb. Similar problem exists at the exhaust port where a reflected wave is needed to stuff the charge back into the combustion chamber when it would just as soon follow the exhaust gas right on out the pipe until the piston closes the exhaust port. One of the reasons Rotax has come to dominate the market for two stroke engines, IMHO, is that they have offered a package that works right out of the box as long as the installer does two things, break the engine in per the table Rotax puts in the installation manual and set the prop for the right loading. It's that simple. The only mod I have ever had to do is drop the needle one notch. Look at the Hirth as the counter example. I had one go round with them and that was enough. The customer absolutely swore the distributor set up the jetting in the carb, and I believe him only because further talk revealed him to be an absolute moron about anything mechanical and removed all question of why he wore velcro closure shoes. Of course the distributor disowned the jet settings I found in the carbs and could tell me nothing about the cut and paste exhaust. Of course they do have a 1000 hour TBO, but I don't think that actually includes engine run time. Anyway, thanks for writing back. Do you still fly the balloon? That article you sent me was a hit with my EAA chapter. Rick On Thu, Aug 19, 2010 at 5:02 PM, rparigoris wrote: > rparigor@suffolk.lib.ny.us> > > Rick > I agree that 2 strokes can be quite different than 4 strokes when it comes > to carb tuning. For one thing many don't have an exactly flat torque curve > where there is less than optimal combustion taking place at a given RPM > range. It could be that all the burnt exhaust gasses are not being expelled > from the combustion chamber or that some of the fresh charge is blowing > right out the exhaust. The type of exhaust affects power band, as does the > intake tuning. BTW I have had great success adding a canister to intake to > act as a dampener in several cases with this sort of thing that happens. > Yamaha called it a tuned intake. What happens on tune of some 2 strokes is > that instead of only sucking through carb, there is a pulse that shoots back > out carb a little at certain RPMs. This really screws things up. The > canister helps even out this shooting back of airflow. This is usual when > engine is out of ideal power band where you are getting a nice fresh charge > in cylinder. I agree that! > first and foremost make sure carb is clean and functioning correctly. (You > did remove all jets and make absolute sure no carb snot? Also make sure > number on jets is as specified by Rotax). It's true that loading can affect > this searching mode. On motorcycles, lets take for example a 1972 Kawasaki > H2 3 cylinder two stroke. When you are crusing at 55mph there is little load > on motor and motor is not quite in efficient part of torque curve. It would > do this hunting trick. I made a pilot controllable air jet where I ran the > pilot air screw a little rich with fuel for the 55mph cruise, but you could > lean it a bit of other times when you were in stop and go mode. Worked > great. Anyway if prop is not loading in a specific install, carb adjustment > can quite possible resolve. I forget specifics on motor origin of motor with > this problem, but if motor was tuned for higher altitude operation and is > now operating at a lower altitude, that will cause a leaner mixture. > I also shoehorned a YTZ250 engine in a YZ 80 frame, took tune of motor from > 5 ports and 32mm carb to 7 ports and 42mm flat slide pretty close to > motocross tune. Again had problems with light loading hunting and made a > reach down when riding airscrew adjustment after getting carb set optimal. > Worked great. BTW tuning did in fact include getting optimal taper to jet > needle. > Remember that the exhaust system can greatly effect tune of a two stroke. > If it is a tuned exhaust almost always to get optimal performance carb needs > tweaking if it was originally tuned for only a muffler. Another often > overlooked issue is an exhaust system that changes. On motorcycles with high > time carbon coats inside. A slick trick is to light carbon on fire with a > oxy acetelene torch, then turn off acetelene and only let oxygen into > chamber, watch carbon burn out (cherry red patch). A few taps releases this > fine brown/tan residue after carbon stops burning. I have had a handful of > subtle tuning issues end up being exhaust related. Not only carbon clogging, > but damaged expansion chambers can cause change. > Ron Parigoris > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=309466#309466 > > -- Zulu Delta Kolb Mk IIIC 582 Gray head 4.00 C gearbox 3 blade WD Thanks, Homer GBYM ________________________________ Message 11 ____________________________________ Time: 06:27:56 PM PST US Subject: RotaxEngines-List: Re: 447 analysis From: "dave" David, I think part of your issue is thats you are running too low RPM 447 503 , 582 will run all day at 5800 to 6000 rpm with EGT in a comfortable range. They are made to run in this range and WOT at 6500 to 6800 no problem. Stop worrying. I assume that you have a stock rotax exhaust ? Dave http://www.youtube.com/user/kitfoxflyer Hundreds of videos with 2 stroke Rotax. -------- Rotax Dealer, Ontario Canada http://www.cfisher.com/ Awesome *New Forum * http://rotaxaircraft.com/forum/ Realtime Kitfox movies to separate the internet chatter from the truth http://www.youtube.com/profile_videos?user=kitfoxflyer Read this topic online here: http://forums.matronics.com/viewtopic.php?p=309485#309485 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rotaxengines-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RotaxEngines-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/rotaxengines-list Browse Digests http://www.matronics.com/digest/rotaxengines-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.